Plate heat exchangers are well known and are generally used to transfer heat from one flowing medium to another. Because of their compound construction and usefulness for different tasks, plate heat exchangers are easy to optimize for their intended function and level of efficiency. Plates in the same plate heat exchanger normally have the same design and usually both of the liquid flow paths have the same cross-sectional area of flow through. In situations where media with different viscosities, e.g. water and oil, or when one medium is gaseous in form, e.g. water and steam, are to exchange heat it is necessary that the more viscous of the media, e.g. oil, has as little resistance to flow as possible, or that the gaseous medium, e.g. steam, is provided with a sufficient volume of through flow. For these reasons, it is desirable to increase the cross-section of flow through in one of the flow paths, in this case, the one intended for oil or steam. This enlargement of the cross-section of flow through between every other heat exchanger plate in the plate heat exchanger can be achieved by designing every other plate with spacing devices that form bulges. The spacing devices can be pressed into the plate, but can also be formed by lugs, loops or similar being attached by welding to every other plate, or by the attachment of mouldings between the plates. By instead producing two different types of plate patterns, it is also possible to achieve flow paths with different cross-sections of flow through. Irrespective of the method of achieving the objective, this nevertheless leads to an increase in the cost of the plate heat exchanger, at the same time as the presence of the spacer devices can in some cases have an adverse effect on the liquid flow.